1) Learn 1, 2, 3 point perspective (basics) - books like "Perspective made easy", if you want more advanced stuff "How to draw" by Scott Robertson etc.
2) Learn how to draw/freehand basic forms - boxes, spheres, cones, pyramids - Dynamic Sketching by Peter Han, moderndayjames etc.
3) Learn how to MODIFY basic forms - cut, add, bend, twist, stack. I'd suggest you learn the basics of 3D sculpting, modeling. Another good resource can be Will Weston.
4) Go to
Sketchfab.com, search for an object that you want to draw
5) Break it into basic forms, as basic as possible! If necessary, break them into primary and secondary forms. The key is simplicity! Fit the inside a cube. Tracing the basic forms over the model can be a good exercise.
6) Now pick your angle and draw the model as primitive forms from reference EXACTLY 50 times. With each drawing done, rotate the model and draw it again until you have 50 broken down objects drawn from reference.
7) Now do the same exact thing but without a reference - try to rotate it in your head, try to place it in a scene. Draw one, check reference after, do that exactly 50 times. You can add details if you like, but keep the basic forms in mind.
8) Now do the same thing the next day or even skip a day and try to do it then. Repeat it again until it's in your long term memory.
